| ??? 10/04/04 02:30 Read: times |
#78655 - RE: Simplified and working schematic Responding to: ???'s previous message |
Now the above circuit seems to work 100% flawlessly. The 220 ohm resistor on MISO seems to be necessary. If I remove it it fails 100% of the time. Is that to be expected? Hallo Craig, the 220Ohm resistor could act as filter to prevent sharp edges on MISO from cross coupling to abother line. That's my only explaination. If this is the case, means if signal integrity is degraded by cross coupling, then you could try to use a flat ribbon cable, with every second line connected to ground, and this at both ends of cable! Then, neglecting the 220Ohm resistor would no longer cause your application to fail. ATMEL uses some similar concept. Here either GND or VCC is put between the lines, using a flat ribbbon cable. By the way, where do you place the buffer: Next to AT89S8252 or to printer port? How long is your cable? Which cable do you use? Kai |
